octor Who” is now and always has been a series which is at its most successful when it walks the tightrope between offering up original ideas and revisiting its past successes. The latter is what has kept the franchise going in some capacity (be it television, motion picture, book, comic book, or even audio adventure) since its inception in 1963, but in recent years, it’s the former that has caused the increase in its American viewership – specifically, because “Doctor Who” finally has the budget to match its creativity. Indeed, it’s been that way for several years now, and given that we’re now in the fourth series of the show since its 2005 revival, one might think it old hat to point out how fantastic “Doctor Who” is these days. But while time might heal all wounds (and if there’s anyone who should be aware of time’s nature, it’s the Doctor), you’d be surprised how many people still hear mention of the series and moan about how cheesy it looks. So it never hurts to mention up front that the show looks bloody fantastic.

When we last left the Doctor, he had once again defeated The Master, but he’d also seen the departure of his latest companion, Martha Jones (Freema Agyeman), and to top it all off, the bow of the Titanic had just come crashing through the wall of his trusty TARDIS. As was revealed in the 2007 Christmas special, however, it wasn’t the Titanic but, rather, a luxury space cruiser bearing the same name, come to Earth to observe our “primitive” holiday celebration. It’s always nice to see Kylie Minogue, who guested in the special as a waitress on the ship, and the ending is one that’ll tug at the heartstrings of the more sentimental “Who” fans, but if you’d been watching it when it originally aired on the BBC, you’d probably have said, “That’s nice, now what’s next?”

Ironically, what was next was a return to the previous year’s Christmas special, “The Runaway Bride,” by reintroducing the title character of the special – Donna Noble – and giving her the honor of being the Doctor’s primary companion for the fourth series. Although Catherine Tate, the actress who plays Donna, is a well-established comedienne in the UK, and a much vaunted one at that, as a “Who” companion, she comes off as a bit grating as often as not. When she’s handed the more emotion-driven moments, she handles them well, but it’s the tendency to fall into the “tough broad” side of her character that grows weary. Not that there’s anything wrong with powerful women, but Tate’s voice has a nails-on-a-chalkboard manner about it when she gets angry. But your personal results may vary, so fair enough on that.

Let’s look at the adventures undertaken by Donna and the Doctor this series, shall we? The alien race known as the Ood, who first appeared in Series Two (“The Impossible Planet), rear their tentacles again in “Planet of the Ood,” where we find that the subservient creatures aren’t doing the bidding of others by choice. A bunch of old-school baddies, the Sontarans, serve as the antagonists in the series’ first two-parter (“The Sontaram Stratagem” / “The Poison Sky”), which also provides an excuse for Martha Jones to return for a few episodes. It will prove unsurprising to anyone who’s been following the Doctor’s adventures over the past few years to learn that Steven Moffat has turned in another intricately-plotted saga with “Silence in the Library” and “Forest of the Dead,” which preys on viewers’ fears of what lurks in the shadows by asking, “What if the shadows themselves couldn’t even be trusted?” There are several one-off episodes which prove enthralling as well, including a locked-room mystery with the queen of the genre herself, Agatha Christie (“The Unicorn and the Wasp”), a Hitchcock-ian thriller on an alien planet (“Midnight”), the introduction of the Doctor’s daughter to the series mythos (appropriately entitled “The Doctor’s Daughter”), and a trip into an elaborate alternate history which cribs the general concept of “It’s A Wonderful Life” by asking, “What if Donna had made a right turn instead of a left turn?” It’s this episode – “Turn Left” – which gives viewers what they’ve been teased with all series long: the return of Rose Tyler (Billie Piper).

The final two episodes of the season – “The Stolen Earth” and “Journey’s End” – feel more like a finale (like, a permanent one) than any season closers in recent memory. Part of that may come from the knowledge that Tennant’s tenure as the Doctor is entering its final stages (the announcement of his imminent departure came after the completion of this series), but it’s mostly because of the cast of guest characters. In the Earth’s darkest hour, the Doctor is nowhere to be found, leaving it to his former cohorts – Sarah Jane Smith (Elizabeth Sladen), Captain Jack Harkness of Torchwood (John Barrowman), Martha, and Rose – to try and save the planet from the terror of the Daleks – again. You can never go wrong with the Daleks as a villain, however, and the added bonus this time comes from the return of Davros, creator of the Daleks, who had not been seen in a “Who” adventure since 1988’s “Remembrance of the Daleks.”

The conclusion of the appropriately-titled “Journey’s End” finally brings Rose’s story to an end that doesn’t leave us constantly hoping for a return appearance, but it also finds the Doctor leaving behind all of his companions and setting off on his own. Leave it to Russell T. Davies to leave “Doctor Who” by bringing it full circle from where he found it. (You may recall that when we first saw The Ninth Doctor, played by Christopher Eccleston, he was all by his lonesome as well.) Now that Davies is stepping down and passing the reigns of command to the aforementioned Mr. Moffat, it’s anyone’s guess what we’ll have to look forward to, but given the success of Series Four, we’re chomping at the bit to find out.

Special Features: Sure as anything, one of these days, the BBC will release a “Doctor Who” set which is lacking in special features, but it’s not happened yet. “The Complete Fourth Series” is once again packed to the rafters with bonus material, starting with the inclusion of audio commentaries and deleted scenes from every single episode. From there, we get “Children in Need: Time Crash,” the charity special which leads directly into “Voyage of the Damned,” but more importantly, it teams David Tennant with one of his predecessors in the role: Peter Davison, who played the Fifth Doctor (1981 – 1984). It’s short – only seven minutes long – but it’s equally funny and sentimental, and for fans, it’s almost worth the price of admission by itself. Beyond that, Tennant offers up his Video Diary in two segments (one on the first disc and one on the last), there’s three hours’ worth of “Doctor Who Confidential.” Lastly, we get “The Journey (So Far),” where cast and crew reminisce, but it’s predominantly a well-deserved opportunity for Davies to muse over his four series of “Doctor Who.”